1. Field of the Invention
The present invention relates to a trap apparatus, and more particularly to a trap apparatus optimum for trapping a material gas discharged from a vapor deposition apparatus for depositing in a vapor phase thin films of high-dielectric or ferroelectric such as barium/strontium titanates on substrates.
2. Description of the Related Art
Recently, in the semiconductor manufacturing industry, the integration of integrated circuits has been improved remarkably, and the research and development activities of DRAM are being intensively carried out in anticipation of gigabit order DRAMs which will replace current megabit order DRAMs. The capacitor element having a large capacity per unit area is needed to produce such DRAMs. As a dielectric thin-film material for producing elements having such a large capacity per unit area, in place of silicon oxide or silicon nitride having dielectric constant less than 10, a metallic oxide film material such as tantalum pentaoxide (Ta2O5) having dieelectric constant of approximately 20, or barium titanate (BaTiO3) or strontium titanate (SrTiO3) or barium strontium titanate having dielectric constant of approximately 300 is considered to be a promising thin-film material. Further, a ferroelectric material having a higher dielectric constant is also considered to be a promising thin-film material.
In addition to the above, as a wiring material, copper which has a value of resistance lower than aluminum and a superior resistance against electromigration is considered to be a promising material. As a material for gate insulating film, BiVO, Bi4Ti4O12, YMnO3, ZnO, ZnS, and CdS are considered to be a promising material. As an electrode material having a perofskite structure, SrRuO3, BaRuO3, IrO, and CaRuO3 are considered to be a promising material. As a material for a barrier layer or a buffer layer, MgO, Y2O3, YSZ, and TaN are considered to be a promising material. As a superconductivity material, Laxe2x80x94Baxe2x80x94Cuxe2x80x94O, Laxe2x80x94Srxe2x80x94Cuxe2x80x94O, Yxe2x80x94Baxe2x80x94Cuxe2x80x94O, Bixe2x80x94Srxe2x80x94Caxe2x80x94Cuxe2x80x94O, Tlxe2x80x94Baxe2x80x94Caxe2x80x94Cuxe2x80x94O, and Hgxe2x80x94Baxe2x80x94Caxe2x80x94Cuxe2x80x94O are considered to be a promising material.
As a process for depositing thin films of such material, a chemical vapor deposition (CVD) process is expected to have a good prospect.
FIG. 6 shows a chemical vapor deposition apparatus for depositing thin films of high-dielectric or ferroelectric such as barium/strontium titanates. The vapor deposition apparatus comprises a vaporizer 10 for vaporizing a liquid material, a hermetically sealable reaction chamber 14 disposed downstream of the vaporizer 10 and connected to the vaporizer 10 through a material gas passage 12, and a vacuum pump 18 disposed downstream of the reaction chamber 14 and provided in an evacuation passage 16. An oxidizer gas pipe 20 for supplying an oxidizer gas such as oxygen is connected to the reaction chamber 14.
In the vapor deposition apparatus having the above structure, a substrate W is placed on a stage 22 for holding and heating the substrate W, and a mixture of material gas and oxidizer gas is ejected over the substrate W from nozzles 26 of a gas supply head 24 while keeping the substrate W at a predetermined temperature, thereby depositing a thin film on a surface of the substrate W. In this case, it is necessary to supply the material gas stably to the substrate W in the reaction chamber 14. The material gas is produced by liquidizing Ba(DPM)2, Sr(DPM)2 or the like which is solid at room temperature, mixing the liquidized substance with organic solvent such as tetrahydrofuran (THF), and vaporizing the obtained mixture by the vaporizer 10.
Gases discharged from the reaction chamber 14 contain unconsumed material and reaction by-product having a high sublimation temperature, and hence the unconsumed material and the reaction by-product are solidified during pressure rise and deposited on the interior of the vacuum pump 18, resulting in a malfunction of the vacuum pump 18. In order to prevent this deposition on the interior of the vacuum pump, as shown in FIG. 6, a trap apparatus 30 is provided at the upstream side of the vacuum pump 18 in the evacuation passage 16 to remove components, in the discharged gases, having a high sublimation temperature and a low vapor pressure. The pipe interconnecting the reaction chamber 14 and the trap apparatus 30 is provided with a temperature adjusting device 28 comprising a mantle heater or the like in the same manner as the material gas supply passage 12.
Conventionally, as shown in FIG. 7, the trap apparatus 30 comprises a trap unit 34 having a spiral baffle plate 32 for forming a spiral fluid passage, a trap container 36 for housing the trap unit 34, an inlet pipe 38 connected to the upper end of the trap container 36, and an outlet pipe 40 connected to the bottom of the trap container 36. The trap apparatus 30 is connected to the evacuation passage 16 by quick couplings 42a and 42b. The trap apparatus 30 has a cooling medium flow passage 44, at the central part thereof, through which a cooling medium cooled to a temperature lower than the condensing temperature of the components, to be trapped, having a low vapor pressure flows. Thus, the components having a low vapor pressure in the discharged gases which have entered the trap container 36 through the inlet pipe 38 are trapped and removed by the trap unit 34 while the discharged gases flow along the baffle plate 32, and hence only the components having a high vapor pressure are led to the vacuum pump 18 through the outlet pipe 40 and the evacuation passage 16 (see FIG. 6).
However, in this trap apparatus, the components having a low vapor pressure such as the unconsumed material are condensed to become powdery substances in the trap container, and the produced powdery substances are gradually deposited on the surface of the trap unit. These deposited solid substances, if counterflow occurs, or the supply amount from the upstream side is abruptly decreased or is stopped under change of conditions in the evacuation system, form particles which will flow into the reaction chamber and deposit on the substrate, resulting in deteriorating quality of a produced film.
It is therefore an object of the present invention to provide a trap apparatus which can reliably trap components having a low vapor pressure in gases discharged from a processing apparatus such as a chemical vapor deposition apparatus and prevent the trapped components from being scattered around.
According to a first aspect of the present invention, there is provided a trap apparatus disposed downstream of a vacuum process chamber. The vacuum process chamber is for processing a substrate. The trap apparatus is for trapping a component having a low vapor pressure contained in a gas discharged from the vacuum process chamber. The trap apparatus comprises a trap container for introducing the gas discharged from the vacuum process chamber, and a cooling device provided in the trap container for cooling the gas to a temperature equal to or lower than a condensing temperature of a gas component which is contained in the gas and easily liquidized.
According to the present invention, the discharged gas introduced into the trap container is cooled by the cooling device, and a gas such as a solvent gas (gas generated from solvent by vaporization), which is contained in the material gas and easily liquidized, is condensed in the trap container, and thus the condensed substances are contained in deposited substances in the trap container. Therefore, the deposited substances in the trap container are moistened, and hence adhesion between the deposited substances and the inner surface of the trap container and cohesion of the deposited substances are heightened. Thus, the deposited substances are prevented from being removed from the inner surface of the trap container and the like, thus preventing generation of particles.
According to a second aspect of the present invention, there is provided a trap apparatus disposed downstream of a vacuum process chamber. The vacuum process chamber is for processing a substrate. The trap apparatus is for trapping a component having a low vapor pressure contained in a gas discharged from the vacuum process chamber. The trap apparatus comprises a trap container for introducing the gas discharged from the vacuum process chamber, and a solvent supply device for supplying a solvent, which is hard to be volatilized, into the trap container.
According to the present invention, by supplying the solvent to the deposited substances in the trap container, the deposited substances in the trap container are moistened, and hence adhesion between the deposited substances and the inner surface of the trap container and cohesion of the deposited substances are heightened. Thus, the deposited substances are prevented from being removed from the inner surface of the trap container and the like, thus preventing generation of particles. As the solvent which is hard to be volatilized, such material as to be liquid under vacuum in the trap container and as to keep a desired degree of vacuum in the processing chamber is selected. By spraying the solvent or scattering the solvent in the trap container, absorption reaction between gas and liquid may be accelerated.
According to a third aspect of the present invention, there is provided a trap apparatus wherein the solvent which is hard to be volatilized is selected from a solvent which is used as a solvent of material including butyl acetate, tetrahydrofrane, or lutidine, a solvent which is used as adduct of material including tetraglymes, toluenes, or tetraenes, or a solvent which is used as a ligand of material including dipivaloylmethane.
According to the present invention, a component having a low vapor pressure in the discharged gas introduced into the trap container is trapped in the liquid solvent stored in the solvent storage, and hence scattering of the trapped substances can be prevented.
In a preferred aspect, the solvent which is hard to be volatilized is selected from a solvent which is used as a solvent of material including butyl acetate, tetrahydrofrane, or lutidine, a solvent which is used as adduct of material including tetraglymes, toluenes, or tetraenes, or a solvent which is used as a ligand of material including dipivaloylmethane. Thus, even if the solvent flows back to the reaction chamber, it does not affect adversely quality of the deposited film.
According to a fourth aspect of the present invention, there is provided a thin-film vapor deposition apparatus comprising: a vaporizer for vaporizing a liquid material; a reaction chamber disposed downstream of the vaporizer; a vacuum pump disposed downstream of the reaction chamber; and a trap apparatus provided in an evacuation passage extending from the reaction chamber to the vacuum chamber, the trap apparatus comprising: a trap container for introducing the gas discharged from the vacuum process chamber; and a cooling device provided in the trap container for cooling the gas to a temperature equal to or lower than a condensing temperature of a gas component which is contained in the gas and easily liquidized.
According to another aspect of the present invention, there is provided a thin-film vapor deposition apparatus comprising: a vaporizer for vaporizing a liquid material; a reaction chamber disposed downstream of the vaporizer; a vacuum pump disposed downstream of the reaction chamber; and a trap apparatus provided in an evacuation passage extending from the reaction chamber to the vacuum chamber, the trap apparatus comprising: a trap container for introducing the gas discharged from the vacuum process chamber; and a solvent supply device for supplying a solvent, which is hard to be volatilized, into the trap container.
According to still another aspect of the present invention, there is provided a thin-film vapor deposition apparatus comprising: a vaporizer for vaporizing a liquid material; a reaction chamber disposed downstream of the vaporizer; a vacuum pump disposed downstream of the reaction chamber; and a trap apparatus provided in an evacuation passage extending from the reaction chamber to the vacuum chamber, the trap apparatus comprising: a trap container for introducing the gas discharged from the vacuum process chamber; and a solvent storage provided in the trap container for storing a solvent, which is hard to be volatilized, in a liquid condition.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrates preferred embodiments of the present invention by way of example.